Rb1 then Kf1 if Rg8 is played

Some comments:

1. Rg3 B:g3 and Black is winning.

2. Kh1 Rg8 2. R3e2! vacates e3 for a devastating check, for example 2...Qb6 3. Qe3+ Kg7 (3...Kh5 4. Bf3+ K{h4 5. Qh6#) 4. Rg1+ Kf8 5. Qh6+ wins a Rook.

I'm not sure what the best defense for Black after Kh1 is, but White has a whole lot of threats. I'm pretty sure Yancey is right, Black is going to have to give up material to get his K out of that box.

For example, 1...Rdd8 2. Qf3 (threatening Q:f6) f5 3. B:f5 and the e-pawn is pinned.

Or 1...Kg7 2. Rg1+ Kf8 3. Rg1+ Kf8 4. Q:f6 and white has the powerful threat of Rg7-h7-h8

Yancey if Kh1 first black can play...1.Rg8

I 'd try Rg3 first to take the g file with the queen

No one posted it, but 1.Kh1 opens the key square of g1 for the rook. Black will have to give up material to prevent getting mated.

It took me a long time to find this one, but seems obvious now that I have. The first has a strong purpose, but I was blind to it for quite a while.